Multiple realities
(covers information from several alternate timelines)
A prenatal exam was a type of medical examination given to pregnant mothers.
In an alternate timeline, Tom Paris recalled listening to Linnis Paris' heartbeat with his wife Kes at a prenatal exam. (VOY: "Before and After")
In 2370, Doctor Beverly Crusher examined a heavily pregnant Spot. (TNG: "Genesis")
In 2372, Ensign Samantha Wildman was one of two visitors to USS Voyager's sickbay during a particular twenty four hour period that Danara Pel was there, having come for her regular prenatal visit. (VOY: "Lifesigns")